Czech spiders specialist raises alarm over species extinction

According to a recent study, some three percent of the country's
spider species have died out and about 50 percent are threatened with
extinction. What are the reasons behind the spiders' disappearance?
And is it true that there are poisonous spiders migrating to the Czech
Republic from the south of Europe?

Photo: Martin Němec
These are just some of the questions I put to biologist Milan Řezáč of
the Crop Research Institute, who is one of the authors of the study. But I
first wanted to know just how threatened spiders in the Czech Republic are:

“Currently we know about 27 species that have probably gone extinct in
the Czech Republic and there are another 92 that are close to extinction,
which means that they will probably die out in the near future. So I would
consider the situation to be really dangerous.

“But of course it depends on your point of view. Some people are more
interested in historical monuments. People are horrified when they see
videos of IS members destroying archaeological sites.

“But let me remind you that while these sites are about 2,000 years old,
every single spider species is several million years old, so in my point of
view it is really sad that we are losing the variety of species and I
definitely consider it a serious problem.”

How long have you been monitoring the situation?

“The first data about spider fauna in the Czech Republic is about 200
years old. But of course the research is getting more and more detailed
with time, so I would say that for the past four decades we have had really
detailed information.”

How long have the spiders been threatened?

“I would say that majority of species that are now considered extinct
have disappeared over the past fifty years. It is probably related to the
change of farming in this country, which started with collectivisation of
Czech farms during Communism.

“There was a tendency to make fields larger and to eliminate the
habitats surrounding the fields that were actually harbouring majority of
the species. But this trend has accelerated in recent years and we can
really see the species disappearing from our landscape.”

What are the other major threats to spider populations?

“Every single spider species is several million years old, so I think it
is really sad that we are losing the variety of species and I definitely
consider it a serious problem.”

“There are some, let’s say more cryptic reasons why species disappear,
for instance the overuse of agrochemicals such as pesticides. But really
the main cause of losing the diversity is changing of the habitat structure
of our landscape.

“Let me compare our nature to a garden. When you don't manage your
garden, many species will disappear, and the same thing happens in nature.
The gardeners in central Europe used to be big animals, mainly herbivores,
who were grazing the grass and allowed the species who were weak in
competition to sustain there.

“Originally these big mammals were wild and later people replaced them
with domesticated animals, who did the same job. But nowadays, this kind of
management is not interesting to people and it causes an overwhelming
overgrowth of landscape with plants and aggressive grasses that really push
away many species.”

Would people actually notice several spider species going extinct? What
are the consequences of their disappearance?

“Every species is connected to the other, so when one species dies out
it affects the others. So for instance parasites that live off these specie
die out as well, the predators who feed on them are also harmed.

“On the other hand the population of the spiders’ prey expands, which
is something we should be concerned about. Because spiders eat mainly
insects and many insects are actually pests.

“So when the spiders are disappearing, there are outbreaks of pests and
it has been scientifically proven that a rich community of spider species
is more able to deal with pests on crops than just a few species.”

Do they encounter the same problems in the rest of Europe?

“It is actually a problem that concerns the whole of Europe, but there
are some differences. For instance in Western Europe there is more advanced
nature conservation so they know more about biology of particular species
and they already do something to protect them.

“There are also countries with very different socio-economic situation,
such as in the south of Europe, where traditional farming is still present.
So species that are already extinct in the Czech Republic can still be
found in other parts of Europe.”

Are Czechs doing something to reverse the trend? Are there some
initiatives that specialise in protection of spiders?

“Unfortunately we are at the very beginning but you can already see some
activities. There are several spider species which were suggested to be
protected by law.

“There are some nature reserves that were established with the aim to
protect endangered spiders. One of those is actually in Prague, a small
wetland in Klánovický les in the eastern part of Prague. And there are
also some organisations that aim to re-introduce traditional ways of
farming to the landscape.

“The goal is to manage the landscape as a garden, to cut the grass, to
keep the habitat open, to harvest the biomass and to eliminate the overuse
of fertilisers. Actually it is interesting that the result is something
that people would consider a beautiful landscape. So spiders actually like
what we consider beautiful.

“The problem is that people, at least in the last decades, lost the
ability to see the beauty of their countryside and they prefer to pay for
expensive holidays abroad. They don't seem to care much about what is
going on beyond their houses.”

How many spider species can actually be found on the territory of the
Czech Republic?

“There is just a small number of species living in the Czech Republic
that can really bite you and these don't cause any serious
consequences.”

“We know about almost 900 species in the Czech Republic, which is a
pretty high number. All over the world we know about 50,000 spiders but the
number is probably much higher, since some areas, such as tropical
rainforests, are not very well researched. But the Czech Republic is one of
the best researched countries as far as spiders are concerned.

Why is that?

“It’s a historical coincidence. We had some scientists who were very
active in studying spiders. I would say that Britain is the best researched
country in terms of spiders and we are the second best.”

Are there any locations that are particularly rich in spider populations?

“Spiders like regions that are variable in habitats, so landscapes with
a strong relief are suitable for them. So in central Bohemia it would be
the region of Křivoklát, in north Bohemia it would be the Krkonoše
mountains and in south Moravia it would be Pálava.

“South Moravia is really rich in species because there are many
thermofilic species that live mainly in the Balkans but their border of
distribution reaches up to south Moravia. Interestingly even Prague is very
rich in spider species. In Prague we have around 500 species, which is a
lot.”

Are there any poisonous spiders living in this country? I have heard that
there are certain species moving from southern Europe.

“No, spiders are still safe. To be honest almost all of the spiders
living in the Czech Republic have a venom gland. But the venom is adapted
to kill or paralyse their prey, usually insects, and it is not harmful to
mammals. There is just a small number of species that can really bite you
and these don't cause any serious consequences. I would compare it to
the sting of wasps or bees.

Photo: Martin Němec
“There are some species that can cause some trouble, for instance velvet
spiders, very rare species living in rocky steppes and in slopes of rivers.
I was bitten by them several times when I studied them and it cause me very
fast heart beat and my face turned purple, but luckily it lasted only for
about an hour.

“Another case would be the only spider living in water, Argironeta
Aquatica. This spider is also large and it can bite you, but you would be
really lucky to encounter it, since waters in the Czech Republic are really
polluted nowadays and there are only a few lakes with clean enough water to
harbour the species. So it's really difficult even for an
arachnologist to find them.”

Still, has this migration of southern European spiders actually taken
place?

“There are some cases of recent migrations to our region and it is
interesting that all these spiders have something in common. They like
warmer environment so it seems that it is really related to global warming.

“Some of them are large and some of them can bite. You. There is one
species, it is called Cheiracanthium Punctorium, in Czech it is
zápřednice jedovatá, which means a venomous spider. This spider can
cause something like a bee sting so there is no reason to be afraid of
spiders in the Czech Republic.”

Finally, you have recently published, along with your colleagues, a book
about spiders. Can you tell me more about it?

Photo: Martin Němec
“It is an atlas of Czech spiders which covers all the nearly 900 species
living in the Czech Republic. And I think none of the other European
countries has such a comprehensive atlas, so you can get a really good idea
of how diverse the spiders are.

“I hope the book will give the wider public a better insight into the
world of spiders. And I would be really happy if some small boy or a girl
would buy the atlas and become a fan of spiders. This is the main reason
why we published the book.”